Corrections will now reduce the number of double bunks from 88 to 44, and spend $10 million on a facelift of the women's prison.

"Some of the challenges faced at Arohata are the direct result of the need for us to rapidly increase prison capacity in response to a 40 percent rise in the women's prisoner population in the last two years," chief custodial officer Neil Beales said.

"We have to take prisoners from the courts, we can't turn them away at the gates because we don't have any space, so we recognise that the Ombudsman was concerned about that, but equally where do we put the prisoners? We can't put female prisoners in a male prison."